Plumb bob



Aprifi 29, 1952 L. SUVERKROP PLUMB BOB Filed Oct. 21, 1948 Patented Apr. 29 1952 UNITED ATENT OFFICE PE UM B BOB Lew Suverkrop, Bakersfield, Calif. Application October 21, 1948, Serial No. 55,805

My invention relates particularly to the geometrical instrument known as the plumb bob, used to establish a location vertically above or below a point; and the present improvements apply especially to the precision type of plumb bob used by builders, surveyors, etc. This type of plumb bob is usually made of brass or bronze and is fitted with a replaceable point of steel. These points wear out and occasionally are lost, and either of these conditions may come about when the user is at a location far removed from a source of replacement points. In addition, the winding of the cord on such a plumb bob, after using it, has always presented an annoying problem due to the smooth and tapered surface of the bob and the lack of any means by which one may start to wrap the cord neatly and securely anywhere on the bob. Lacking any such means, a common method has been to kite-string the cord from end to end of the bob. This and other methods of disposing of the cord when not in use are untidy, and take unnecessary time in wrapping and unwrapping the cord.

One of the objects of this invention is to provide a place within the bob itself for carrying an extra replacement point and pin or other means for removing and inserting such points. Another object is to provide a convenient means by which the cord may be directly, neatly, and securely wrapped on the plumb bob. These and other objects will be apparent from the following description and the accompanying drawings,

in which Fig. 1 is an elevation of a plumb bob made according to this specification;

Fig. 2 is a cross section taken along the longitudinal axis of the plumb bob shown in Fig. 1;

Fig. 3 shows the manner of wrapping the cord on the bob, making use of this invention; and

Fig. 4 shows another embodiment of one of the details of this invention.

The plumb bob consists of a body I of common bulbous form into the lower end of which a replaceable point 2 having a pointed tip is fixed as by screw threads clearly shown in Fig. 1, the point 2- having a threaded shank 2'. The upper end of the body I is fitted with a cap 3 to which the cord 4 is attached. Said cap is provided with a cylindrical cavity 3' which accommodates knot 4' on the end of the cord. The attachment of the cap 3 to the body I is by any common means and the cap is suitably knurled at its top, for example, and is otherwise fitted so that, while it will remain properly in place when the bob is in use, it may be removed and replaced at any 2 Claims. (01. 33-2'17) time, using only the fingers. In eifect, the cap comprises a shank, for purposes to be described, extending upward in use from the upper end of the body I.

The body l is drilled and bored to provide a cavity 5 to hold the replacement point 6 and the pin 1. As shown in the drawing, access to the replacement point t and the pin 1 is readily accomplished by removing the cap 3. By making the cavity 5 close in size and shape to that of the point 6 and pin 1 which are carried within it, the size of the bob need not be increased ap= preciably because the weight of the metal removed in forming the cavity 5 will be nearly equalled by the parts 6 and I carried within it. It will also be seen that the threaded shank 6' of replacement point 6 fits readily within the cavity 3' of the cap, so that point 6 is confined between cap 3 and the walls of the conical upper portion of cavity 5, whereby the pointed tip of the point 6 will not be subjected to harm while stored within the cavity 5.

It is preferable to have the cavity 5 extend through the length of the body I so that inthe event one or the other of the contained parts 6 and 7 should become firmly lodged in; it,-'as' by rust, they may be readily removed. By packing the parts in grease any difiiculty of rust will be obviated and the pin 1 will be held in place by the grease should the point 2 be accidentally lost, while allowing the parts 6- and I- to be readily re: moved whenever desired. With this construction, the plumb bob user will have, at all times whenever and wherever he may be working with the plumb bob, and regardless of his isolation from a usual source of supply, the means for replacing the point 2 with a new replaceable point.

The cap 3 is provided with a projection 8 near the place where the cap 3 shoulders against the body I. This projection 8, as shown in Fig. 2, is a short pin permanently lodged in a hole drilled in the cap 3. The mass of this pin is so small, compared with the total mass of the bob, and is. so close to the axis of the bob, the bob will not be appreciably thrown out of balance by use of only one such projection 8. But it is understood that two or more opposed projections 8 may be used if it be desired to obtain perfect balance.

As indicated in Fig. 3, when it is desired to wrap the cord on the shank of the bob comprising cap 3, the body of the bob is held with one hand and, after starting the cord around the projection 8 with the thumb of the other hand so as to hold a portion of the cord caught or fixed relative to the shank and body, the cord is wrapped rather firmly about the shank at the shoulder where it joins the body I. If the cord is extensive in length, it will not only be wound upon the shank but also onto part of the body I. Coming to the end of the cord, the cord end is quickly secured by pulling on said end with sufficient force to cause the part of the cord near the end to draw down between the wraps of cord on the shank. This secures the cord against unintentional unwrapping, and at the same time leaves the end in place for quickly unwrapping the cord for the next use of the bob.

It is understood that the purposes of the projection 8 will be served by constructing it in a different form. For example, the cap 3 may be formed by a lathe process so that an annular ring 9 is formed on the surface of the cap 3, the cross section of this ring being about equal in area to that of the projection 8 as it extends outward from the cap 3 in Fig. 2, and then milling one or more slots 10 across this annular ring to its full depth where it joins the outer surface of the cap 3. Such a construction is shown in Fig. 4.

In the embodiment shown in Fig. 4, when the cord is to be wound about the cap 3, the cord is first led from the upper end of the cap, is passed through the slot l in ring 9, and then is wound around the cap as explained above relative to the other embodiment of the invention.

It is to be understood that some of the details disclosed in this specification are applicable to and may be used in other devices, and may be used in entirely different arts. Moreover, while I have illustrated and described preferred forms of construction. I do not wish to limit myself to the precise details of structure shown in the drawings, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.

- I claim-as my invention:

1. A plumb bob comprising in combination, a body having a generally conical cavity extending thereinto from one end and terminating at its inner end in a substantially cylindrical portion, a tipped conical point substantially complementary to said conical cavity and detachably secured to the other end of said body by means of a threaded shank on said point extending in a direction opposite to the tip thereof, and a cap removably secured to said one end of said body and provided with a cavity extending thereinto from the inner end of said cap, said cavity in said cap being shaped to accommodate the shank of a replacement point similar to said tipped conical point and hold the same disposed longitudinally of said body with the tipped end thereof within said conical cavity within said body and free from damaging movement therein.

2. A plumb bob comprising in combination, a body having a generally conical cavity extending thereinto from one end and terminating at its inner end in a substantially cylindrical portion, a tipped conical point substantially complementary to said conical cavity and detachably secured to the other end of said body by means of a threaded shank on said point, said shank extending away from an annular shoulder on said point in a direction opposite to the tip thereof, and a cap removably secured to said one end of said body in coaxial alignment with said conical cavity therein and provided with a cavity extending thereinto from the inner end of said cap, said cavity in said cap being shaped to accommodate the shank of a replacement point similar to said tipped conical point and the inner end of said cap being disposable adjacent the annular shoulder of said replacement cap to hold the replacement point disposed longitudinally of said body and the tipped end thereof within said conical cavity and free from damaging movement therein.

LEW SUVERKROP.

BEFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 267,655 Vajen Nov. 14, 1882 630,262 Nacke Aug. 1, 1899 1,025,828 Paul May '7, 1912 1,060,855 Pipher May 6, 1913 1,147,304 Byron July 20, 1915 1,336,289 Fagrie Apr. 6, 1926 1,596,882 Langsner Aug. 24, 1926 FOREIGN PATENTS Number Country Date 223,159 Great Britain 1924 

